Employee Benefits - Asset Target Allocations Prescribed by Pension Funds' Investment Policies (Details)	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	100.00%
Equity Securities, United States [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	5.00%
Equity Securities, International [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	4.00%
Fixed Income Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	81.00%
Defined Benefit Plan, Real Assets [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	6.00%
Other assets (measured at NAV) [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Target Allocation	4.00%